Pool chlorine calculator
This pool chlorine calculator tells you how much chlorine to add to raise the free chlorine from your test reading to your target, or to shock the pool. Choose liquid chlorine, calcium hypochlorite, dichlor, trichlor or lithium hypochlorite. One ppm in 10,000 gallons equals about 1.3 oz of available chlorine, divided by the strength of the product.
Example: Pool volume in: US gallons · Pool volume 10,000 gal / m³ · What do you want to do: raise chlorine to a target · Current free chlorine 1 ppm · Target free chlorine 3 ppm · Chlorine product: Liquid chlorine (12.5%) → Chlorine to add: 20.5 fl oz of liquid chlorine. Source: Los Angeles County Department of Public Health – Swimming Pool Service Technician’s Study Guide: available chlorine of pool chemicals, dosing formula, superchlorination (read 09.10.2026). Updated: .
How it is calculated
To raise a 10,000-gallon pool from 1 to 3 ppm free chlorine you need about 2.7 oz of available chlorine: 20.5 fl oz of 12.5% liquid chlorine, 4.1 oz of cal-hypo (65%), 4.5 oz of dichlor or 3 oz of trichlor.
How the pool chlorine calculator works
1 ppm is 1 mg per litre, or 1 gram per cubic metre. The amount of product is: ppm increase × volume ÷ strength. The Los Angeles County pool technician study guide writes the same rule as ppm = pounds of product × % strength × 1,000,000 ÷ (gallons × 8.3). For liquid chlorine the percentage means grams of available chlorine per 100 ml.
| Product | Available chlorine | +1 ppm in 10,000 gal |
|---|---|---|
| Trichlor tablets | 90% | 1.5 oz |
| Calcium hypochlorite | 65% | 2.1 oz |
| Dichlor | 60–65% | 2.2 oz (at 60%) |
| Lithium hypochlorite | 35% | 3.8 oz (0.24 lb) |
| Liquid chlorine | 10–15% | 10.2 fl oz (at 12.5%) |
The strengths are those given in the LA County study guide; always use the figure on your label.
What chlorine level should a pool have?
The CDC recommends at least 1 ppm free chlorine in home pools, at least 2 ppm when you use cyanuric acid or stabilized products (dichlor, trichlor), at least 3 ppm in hot tubs, and pH 7.0 to 7.8. Above pH 8 chlorine kills germs much more slowly. To shock (superchlorinate) a pool, add free chlorine equal to ten times the combined chlorine.
Examples
- 10,000 gal, 1 → 3 ppm: 20.5 fl oz of liquid chlorine or 4.1 oz of cal-hypo.
- 10,000 gal, +1 ppm with lithium hypochlorite: 0.24 lb (3.8 oz), as in the study guide’s table.
- 30 m³, 0.5 → 3 ppm: 115 g of cal-hypo or 600 ml of liquid chlorine.
- Shock 30 m³ at 0.4 ppm combined chlorine: +4 ppm = 185 g of cal-hypo or 960 ml of liquid chlorine.
To work out your pool volume use the pool volume calculator.
Limits
The result is the calculated dose. Sunlight, swimmers, temperature and cyanuric acid use up or bind chlorine, so test at least twice a day. Liquid chlorine weakens in storage. Never mix chlorine products with each other or with acid, and follow the safety instructions on the package.
Frequently asked questions
How much liquid chlorine to raise 1 ppm in 10,000 gallons?
About 10.2 fl oz of 12.5% liquid chlorine. For 10% chlorine it is about 12.8 fl oz.
How much shock do I need for my pool?
For breakpoint shocking add ten times the combined chlorine. With 0.4 ppm combined chlorine that is +4 ppm: in 10,000 gallons about 8.2 oz of 65% cal-hypo or 41 fl oz of 12.5% liquid chlorine.
What should my pool chlorine level be?
CDC: at least 1 ppm free chlorine, at least 2 ppm with stabilizer (dichlor or trichlor), and at least 3 ppm in a hot tub.
What pH should a pool be?
The CDC recommends 7.0 to 7.8. Above 8.0 chlorine works much worse; below 7.0 pipes and equipment corrode more easily.
How do I convert ppm to grams?
1 ppm is 1 gram of available chlorine per cubic metre (1,000 litres). Divide by the product strength: 1 g of chlorine is 1.54 g of 65% cal-hypo.
Why are dichlor and trichlor different?
They contain cyanuric acid, which protects chlorine from sunlight but slows it down. CDC therefore recommends a higher minimum of 2 ppm and advises against them in hot tubs.
Sources and legal basis
- Los Angeles County Department of Public Health – Swimming Pool Service Technician’s Study Guide: available chlorine of pool chemicals, dosing formula, superchlorination (read 09.10.2026)
- CDC – Home Pool and Hot Tub Water Treatment and Testing (10.05.2024): free chlorine ≥ 1 ppm pools, ≥ 3 ppm hot tubs, ≥ 2 ppm with cyanuric acid, pH 7.0–7.8 (read 09.10.2026)
As of: · Editorial policy
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